Epicotyl Dormancy in Viburnum acerifolium (Caprifoliaceae)

Abstract

Abstract Seeds (true seed plus endocarp) of Viburnum acerifolium have underdeveloped linear embryos and deep simple epicotyl morphophysiological dormancy. Seeds mature and are dispersed in autumn, and radicles and epicotyls emerge the following autumn and late autumn-winter, respectively. Embryos in seeds incubated at 25/15 C became fully elongated in 16 wk, whereas those incubated at 5 C hardly grew at all. The optimum continuous temperature regime for both rate and percentage of radicle emergence was 25/15 C. At this regime, however, ≥20 wk were required for radicles to emerge in a high percentage of the seeds. GA3 had little or no effect on radicle emergence. In seeds subjected to a winter → spring → summer → autumn temperature regime in controlled environments, radicles emerged in autumn in the 20/10 → 15/6 C portions of the sequence. In those subjected only to the summer → autumn portions of the sequence, radicles also emerged in autumn at 20/10 → 15/6 C. Thus, in nature, the cold winter season has n...